Preparation method of adsorbent for adsorption separation of n-butene and isobutene

Abstract

The invention relates to the technical field of porous adsorption materials and low-carbon hydrocarbon separation, in particular to a preparation method of an adsorbent for adsorption separation of n-butene and isobutene, and the preparation method comprises the following steps: step 1, preparation of calcium ion modified LTA zeolite: step 1.1, uniformly mixing 8.24 g of powdery instant sodium silicate, 6.4 g of NaOH and 80mL of deionized water in a beaker, and stirring uniformly to obtain calcium ion modified LTA zeolite; stirring and dissolving to obtain a transparent sodium silicate solution. According to the preparation method of the adsorbent for adsorption separation of n-butene and isobutene, after Na < + > is replaced by Ca < 2 + >, the pore window of LTA zeolite is expanded from 0.4 nm to 0.5 nm, isobutene can be repelled while the molecular size of n-butene is matched, n-butene can be reserved in an adsorption column to a great extent in the dynamic adsorption process, isobutene with very high purity can be generated in tail gas, and the service life of the adsorbent is prolonged. The raw materials for preparing the adsorbent material are relatively cheap, so that the preparation cost is very low.

Description

Technical Field

[0001] The present invention relates to the technical field of porous adsorption materials and low-carbon hydrocarbon separation, and specifically to a preparation method of an adsorbent for the adsorption separation of 1-butene and isobutene. Background Art

[0002] n-Butene and isobutene are important basic organic chemical raw materials and have extremely wide applications in modern production and life. At present, the main ways to produce n-butene and isobutene in China include catalytic cracking, steam cracking, and methanol-to-olefins. However, the n-butene and isobutene initially obtained through these processes coexist in the form of mixtures. From the perspective of maximizing resource value, if n-butene and isobutene are separated and utilized specifically, it will be more conducive to the realization of their values. For example, high purity is required for n-butene when it is used as a comonomer in the production of linear low-density polyethylene (LLDPE) and high-density polyethylene (HDPE) resins, while a purity greater than 99% is required for isobutene when it is used in the production of products such as butyl rubber, tert-butylamine, and pivalic acid. Therefore, using various means to purify the original mixed gas to obtain high-purity n-butene and isobutene is crucial for their application and value addition.

[0003] Since the boiling points of n-butene and isobutene are extremely close (266.92 K and 266.25 K respectively), it is relatively difficult to separate them by distillation in industry, and it will also bring certain economic and environmental pressures, which is contrary to the concept of energy conservation and carbon reduction actively advocated in China. Therefore, finding new separation and purification technologies has crucial practical and development significance. Among many gas purification processes, adsorption separation technology, as an alternative separation scheme, is often used to study the separation and purification of C4 hydrocarbons. The adsorption separation process does not involve phase change, requires lower energy consumption, and is also a more economical and environmentally friendly separation strategy compared to separation methods such as distillation.

[0004] Adsorption separation technology mainly uses the differences in adsorption strength, diffusion rate, or molecular size between different adsorbates and adsorbents to achieve separation. According to the separation mechanism, they can be divided into thermodynamic separation, kinetic separation, molecular sieve separation, and framework response separation, etc. To fully exert the efficacy of adsorption separation technology, the core lies in successfully finding a suitable high-efficiency adsorbent. Considering the differences in the kinetic diameters of n-butene and isobutene ( and respectively), it is an ideal situation to separate them kinetically by designing the pore size of the porous material. Zeolites, as a kind of porous adsorbent, show certain potential in the efficient separation of C4 hydrocarbon mixtures. They usually have highly ordered, regular, and adjustable porous structures and can achieve effective screening according to the differences in the kinetic diameter or minimum cross-sectional size of the target components.

[0005] Zeolites contain regular pore structures in one, two, and three dimensions. The three-dimensional network structure is composed of TO4 tetrahedra connected by shared oxygen atoms (such as [SiO4], [AlO4], [TiO4], etc.). The most basic structure in the zeolite framework is SiO4 and AlO4 tetrahedra. [SiO4] maintains electrical neutrality, while [AlO4] has a unit of negative charge, so it needs to combine with cations to balance the charge and maintain electrical neutrality. The general chemical formula is: (M) 2 / n O·Al2O3·xSiO2·pH2O, where M is the metal ion, n is the metal ion valence number, x is the number of moles of SiO2, and p represents the number of moles of H2O. Zeolite molecular sieves not only possess diverse pore structures but also exhibit excellent chemical and thermal stability, enabling them to achieve excellent adsorption and desorption cycles during temperature swing adsorption. This performance has led to their widespread application in gas adsorption separation. Zeolite molecular sieves are also generally inexpensive, and their application in the separation and purification of n-butene and isobutylene can significantly reduce the production cost of the purified gas. Summary of the Invention

[0006] The present invention uses a calcium ion-modified LTA zeolite as an adsorbent and adjusts the micropore size to a range of 0.5±0.1 nm, thereby achieving efficient separation of n-butene and isobutene. To achieve the above-mentioned purpose, the present invention provides the following technical solution: a method for preparing an adsorbent for the adsorptive separation of n-butene and isobutene, comprising the following steps:

[0007] Step 1: Preparation of calcium ion modified LTA zeolite, as follows:

[0008] Step 1.1: Mix 8.24 g of powdered instant sodium silicate, 6.4 g of NaOH, and 80 mL of deionized water in a beaker and stir to dissolve to obtain a transparent sodium silicate solution.

[0009] Step 1.2: Dissolve 6.15 g of sodium metaaluminate, 3.2 g of NaOH, and 40 mL of deionized water to obtain a transparent sodium aluminate solution.

[0010] Step 1.3: Slowly add the sodium silicate solution dropwise to the sodium aluminate solution, stir and mature at room temperature for 24 hours to obtain a gel mixture;

[0011] Step 1.4: Transfer the gel mixture to a polytetrafluoroethylene autoclave and hydroheat at 363 K for 24 h.

[0012] Step 1.5: After the hydrothermal reaction is completed, the reactor is cooled to room temperature, the product is filtered out and washed with deionized water until the pH is neutral;

[0013] Step 1.6: The solid product was dried in an oven at 373K for 12h to obtain the synthesized LTA zeolite powder, which was named LTA-Na. This powder has not been modified with calcium ions yet;

[0014] Step 1.7: Take out 5g of the above-synthesized LTA zeolite powder, add it to an aqueous calcium chloride solution with a concentration of 0.1mol / L, and stir at room temperature for 24h;

[0015] Step 1.8: Filter to obtain the filter residue, and then add the 0.1mol / L aqueous calcium chloride solution to the filter residue again and stir at room temperature for 24h;

[0016] Step 1.9: Filter to obtain the filter residue, thoroughly wash the material with deionized water, and after washing, place it in an oven to dry. The obtained powder is the calcium ion-modified LTA zeolite powder, which is named LTA-Ca 0.1 ;

[0017] Step 2: Based on the above-prepared calcium ion-modified LTA zeolite powder, use bentonite to bond it to prepare zeolite particles for the adsorption separation of 1-butene / iso-butene in a fixed bed. The specific steps are as follows:

[0018] Step 2.1: Take out a certain amount of the calcium ion-modified LTA zeolite powder, add 5% of its mass of bentonite to it, and mix the two evenly;

[0019] Step 2.2: Add a small amount of deionized water to the above mixed powder and stir evenly to make the mixture present a semi-fluid colloidal state;

[0020] Step 2.3: Use a small spoon to dig out some of the colloidal substance and slowly roll it into small balls of appropriate size and spread them one by one on a clean polytetrafluoroethylene disc;

[0021] Step 2.4: Put the disc into an oven to dry for 6h to obtain spherical calcium ion-modified LTA zeolite particles with a size between 3 - 5mm;

[0022] Step 3: Use the formed calcium ion-modified LTA zeolite particles for the adsorption separation of 1-butene / iso-butene. The entire adsorption separation process is carried out at a pressure of 1 bar. The flow rate of each gas is controlled by a mass flow controller (MFC). When the gas enters the adsorption column filled with molecular sieve (inner diameter: 10mm, column length: 65mm) for adsorption, the concentration of each component gas in its tail gas is measured by a gas chromatograph, and the final result is transmitted through an electrical signal. The specific operation steps are as follows:

[0023] Step 3.1: Pack about 500mg of molecular sieve particles into the adsorption column and ensure that the airtightness of the entire adsorption device is good;

[0024] Step 3.2: Open the through-ball valves 1 and 4, close the through-ball valves 2 and 3, turn on the nitrogen gas switch, adjust the nitrogen gas flow rate to 20 mL / min, and allow the nitrogen gas to purge the molecular sieve from top to bottom. Heat the adsorption column to dehydrate and activate the molecular sieve in the adsorption column under a N2 atmosphere at 423 K for 1 h.

[0025] Step 3.3: After the activation is completed, stabilize the temperature of the adsorption column at 298 K, close the through-ball valves 1 and 4, and turn off the nitrogen gas switch. Open the n-butene and isobutene gas cylinder switches, control the flow rates of the two gases to be 10 mL / min respectively, open the through-ball valves 2 and 3, and allow the binary mixed gas to pass through the adsorption column from bottom to top (green route) for adsorption. The tail gas after adsorption enters the gas chromatograph for analysis.

[0026] Step 3.4: Normalize the experimental data obtained from the gas chromatography and plot the breakthrough curve of the concentration of each component versus time.

[0027] First, the preparation of calcium ion-modified LTA zeolite is as Figure 1 shown. First, use the hydrothermal synthesis method to prepare LTA zeolite. First, uniformly mix 8.24 g of powdered sodium silicate, 6.4 g of NaOH, and 80 mL of deionized water in a beaker, stir and dissolve to obtain a transparent sodium silicate solution. Then, mix and dissolve 6.15 g of sodium aluminate, 3.2 g of NaOH, and 40 mL of deionized water to obtain a transparent sodium aluminate solution. Slowly add the sodium silicate solution to the sodium aluminate solution and stir and age at room temperature for 24 h to obtain a gel mixture. Then, transfer the gel mixture to a polytetrafluoroethylene autoclave and hydrothermal at 363 K for 24 h. After the hydrothermal reaction is completed, wait for the autoclave to cool to room temperature, filter out the product and wash it with deionized water until the pH is neutral. Finally, dry the solid product in an oven at 373 K for 12 h to obtain the synthesized LTA zeolite powder, which is named LTA-Na. Then, prepare calcium ion-modified LTA zeolite by the ion exchange method. Add 5 g of LTA-Na to the calcium chloride aqueous solution and mix evenly, stir at room temperature for 24 h, filter out the powder and repeat once, and then thoroughly wash the material with deionized water. The obtained filter residue is the calcium ion-modified LTA zeolite powder. The concentration of the calcium chloride solution during the ion exchange process is 0 - 0.9 mol / L.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] In the present invention, Ca 2+ replaces Na +After that, the pore window of the LTA zeolite expands from 0.4 nm to 0.5 nm, which can match the size of n-butene molecules while excluding isobutene. During the dynamic adsorption process, n-butene can be retained in the adsorption column to a great extent, enabling the production of highly pure isobutene in the tail gas.

[0030] In the present invention, the raw materials for making the adsorbent material are relatively inexpensive, resulting in a very low manufacturing cost. At the same time, the material can withstand high temperatures and is suitable for the temperature swing adsorption process.

[0031] In the present invention, the adsorption separation process can be carried out at normal temperature and pressure, which is very convenient and the operation process is also very simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a flow chart for preparing calcium ion-modified LTA zeolite by hydrothermal synthesis and ion modification in the present invention;

[0033] Figure 2 is a picture of the calcium ion-modified LTA zeolite particles after shaping in the present invention;

[0034] Figure 3 is a schematic diagram of the device for adsorbing and separating n-butene and isobutene mixed gas using calcium ion-modified LTA zeolite in the present invention;

[0035] Figure 4 is an XRD pattern of the LTA zeolite after synthesis and calcium ion modification in the present invention;

[0036] Figure 5 is an SEM image of the calcium ion-modified LTA zeolite in the present invention;

[0037] Figure 6 is a TGA graph of the LTA zeolite after synthesis and calcium ion modification in the present invention;

[0038] Figure 7 is the 87K argon adsorption-desorption curve and pore size distribution graph of the calcium ion-modified LTA zeolite in the present invention;

[0039] Figure 8 is the breakthrough curve graph of the calcium ion-modified LTA zeolite for n-butene and isobutene mixed gas in the present invention;

[0040] Figure 9 is LTA-Ca in the present invention 0.3 cyclic adsorption performance graph for n-butene / isobutene;

[0041] Figure 10 is LTA-Ca in the present invention 0.3 XRD patterns before and after cyclic adsorption. DETAILED DESCRIPTION OF THE INVENTION

[0042] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0043] Embodiment 1

[0044] Step 1: Preparation of calcium ion-modified LTA zeolite, specifically as follows:

[0045] Step 1.1: Uniformly mix 8.24 g of powdered instant sodium silicate, 6.4 g of NaOH, and 80 mL of deionized water in a beaker, and stir and dissolve to obtain a transparent sodium silicate solution;

[0046] Step 1.2: Mix and dissolve 6.15 g of sodium aluminate, 3.2 g of NaOH, and 40 mL of deionized water to obtain a transparent sodium aluminate solution;

[0047] Step 1.3: Slowly add the sodium silicate solution dropwise to the sodium aluminate solution, and stir and age at room temperature for 24 h to obtain a gel mixture;

[0048] Step 1.4: Transfer the gel mixture to a polytetrafluoroethylene autoclave and hydrothermally treat it at 363 K for 24 h;

[0049] Step 1.5: After the hydrothermal treatment, wait for the autoclave to cool to room temperature, filter out the product and wash it with deionized water until the pH is neutral;

[0050] Step 1.6: Dry the solid product in an oven at 373 K for 12 h to obtain the synthesized LTA zeolite powder, which is named LTA-Na. This powder has not been modified by calcium ions yet;

[0051] Step 1.7: Take out 5 g of the above-synthesized LTA zeolite powder, add it to a 0.1 mol / L calcium chloride aqueous solution, and stir at room temperature for 24 h;

[0052] Step 1.8: Filter to obtain the filter residue, and then add the 0.1 mol / L calcium chloride aqueous solution to the filter residue again and stir at room temperature for 24 h;

[0053] Step 1.9: Filter to obtain the filter residue, thoroughly wash the material with deionized water, and after washing, put it in an oven to dry. The obtained powder is the calcium ion-modified LTA zeolite powder, which is named LTA-Ca 0.1 ;

[0054] Step 2: Based on the above-prepared calcium-ion-modified LTA-type zeolite powder, use bentonite to bond it to prepare zeolite particles for the adsorption separation of 1-butene / isobutene in a fixed bed, which specifically includes the following steps:

[0055] Step 2.1: Take out a certain amount of calcium-ion-modified LTA-type zeolite powder, add 5% of its mass of bentonite to it, and mix the two evenly;

[0056] Step 2.2: Add a small amount of deionized water to the above mixed powder and stir evenly to make the mixture present a semi-fluid gel-like state;

[0057] Step 2.3: Use a small spoon to dig out some of the gel-like substance and slowly roll it into small balls of appropriate size and spread them one by one on a clean polytetrafluoroethylene disc;

[0058] Step 2.4: Put the disc into an oven and dry it for 6 h to obtain spherical calcium-ion-modified LTA-type zeolite particles with a size between 3 - 5 mm, and the shape is as Figure 3 shown;

[0059] Step 3: Use the formed calcium-ion-modified LTA-type zeolite particles for the adsorption separation of 1-butene / isobutene. The entire adsorption separation process is carried out under a pressure of 1 bar. Figure 3 is a schematic diagram of the device. The flow rate of each gas is controlled by a mass flow controller (MFC). After the gas enters the adsorption column filled with molecular sieve (inner diameter: 10 mm, column length: 65 mm) for adsorption, the concentration of each component gas in its tail gas is measured by a gas chromatograph, and the final result is transmitted through an electrical signal. The specific operation steps are as follows:

[0060] Step 3.1: Fill about 500 mg of molecular sieve particles into the adsorption column and ensure that the airtightness of the entire adsorption device is good;

[0061] Step 3.2: Open direct-through ball valves 1 and 4, close direct-through ball valves 2 and 3, turn on the nitrogen switch, regulate the nitrogen flow rate to 20 mL / min, so that nitrogen purges the molecular sieve from top to bottom, heat the adsorption column, and make the molecular sieve in the adsorption column remove water and be activated for 1 h under a N2 atmosphere at 423 K;

[0062] Step 3.3: After the activation is completed, stabilize the temperature of the adsorption column at 298 K, close direct-through ball valves 1 and 4, and turn off the nitrogen switch. Turn on the switches of the 1-butene and isobutene gas cylinders, control the flow rates of the two gases to be 10 mL / min respectively, open direct-through ball valves 2 and 3, so that the binary mixed gas passes through the adsorption column from bottom to top (green route) for adsorption, and the adsorbed tail gas enters the gas chromatograph for analysis;

[0063] Step 3.4: Normalize the experimental data obtained in gas chromatography and plot the breakthrough curve of the concentration of each component changing with time.

[0064] Example 2

[0065] Similar to Example 1, the difference is that the concentration of the calcium chloride aqueous solution for modification in Steps 1.7 and 1.8 of Example 2 is adjusted to 0.3 mol / L, and the remaining steps are the same, and it is named LTA-Ca 0.3 . At the same time, add Step 4 to conduct a cyclic adsorption test to test its reuse situation. The test device still uses the Figure 3 device shown, and the specific steps are as follows:

[0066] Step 4.1: After the end of Step 3.4, close the straight-through ball valves 2 and 3, and close the switches of the n-butene and isobutene gas cylinders;

[0067] Step 4.2: Open the straight-through ball valves 1 and 4, open the nitrogen switch, and heat the adsorption column to desorb and regenerate the molecular sieve in an N2 atmosphere at 423K for 4 h;

[0068] Step 4.3: After the regeneration is completed, continue to start Steps 3.3 and 3.4;

[0069] Step 4.4: Repeat Steps 4.1 - 4.3 until the end of the 5th cyclic adsorption.

[0070] Example 3

[0071] Similar to Example 1, the difference is that the concentration of the calcium chloride aqueous solution for modification in Steps 1.7 and 1.8 of Example 2 is adjusted to 0.5 mol / L, and the remaining steps are the same, and it is named LTA-Ca 0.5 ;

[0072] Example 4

[0073] Similar to Example 1, the difference is that the concentration of the calcium chloride aqueous solution for modification in Steps 1.7 and 1.8 of Example 2 is adjusted to 0.7 mol / L, and the remaining steps are the same, and it is named LTA-Ca 0.7 ;

[0074] Example 5

[0075] Similar to Example 1, the difference is that the concentration of the calcium chloride aqueous solution for modification in Steps 1.7 and 1.8 of Example 2 is adjusted to 0.9 mol / L, and the remaining steps are the same, and it is named LTA-Ca 0.9 .

[0076] The XRD patterns of the synthesized and calcium-modified LTA zeolites are as follows Figure 4 shown. The diffraction peak positions and intensities of all samples are basically similar to those of the LTA zeolite, and there are no amorphous peaks, indicating that they have the same crystal structure and maintain a good LTA-type zeolite structure. At the same time, a new diffraction peak appears at 2θ = 25.1° for the calcium-modified zeolite, indicating that Ca 2+ is exchanged with Na + , representing that the calcium modification of Examples 1-5 was successfully carried out.

[0077] Table 1 lists the unit cell parameters and crystallinities corresponding to 6 samples. It can be seen from the table that the unit cell parameters of the zeolite increase to varying degrees after adding Ca 2+ . At the same time, all samples have a high crystallinity, indicating that the zeolite prepared by this method has a high purity and few impurities.

[0078] Table of unit cell parameters and crystallinities of synthesized and calcium-modified LTA zeolites

[0079]

[0080] The SEM images of the calcium-modified LTA zeolites are as follows Figure 5 shown. It can be seen from Figures (a)-(e) that all calcium-modified LTA zeolites maintain a clear cubic morphology, with regular and distinct particles, a smooth and flat surface, and the crystal structure is not damaged due to the calcium ion exchange, having good structural stability. The average size of the Ca-modified LTA zeolite particles is maintained at about 0.8 μm.

[0081] The TGA curves of the synthesized and calcium-modified LTA zeolites are as follows Figure 6 shown. The weights of all samples decrease rapidly between 30°C and 250°C, which is related to the removal of free water in the zeolite pores. From the decrease range, the calcium-modified LTA zeolite has more free water than the unmodified LTA-Na. After 250°C, the weight loss of all samples does not change significantly, and they all maintain more than 80% of their weight at 800°C, indicating that they all have good thermal stability.

[0082] The 87K argon adsorption-desorption and pore size distribution of the calcium-modified LTA zeolite are as follows Figure 7As shown. It can be seen from Figure (a) that the adsorption trend of all calcium-ion-modified LTA zeolites for argon in the low-pressure range is a Type I adsorption isotherm, belonging to the classic micropore adsorption phenomenon, indicating that there are a large number of micropores inside them. As the relative pressure increases, the adsorption amount of argon slowly rises and finally tends to saturation, without an obvious hysteresis loop. It can be seen from Figure (b) that the pore size of calcium-ion-modified LTA zeolite is approximately in the range of 0.4 - 0.6 nm, among which the pore size of LTA-Ca 0.3 is on the smaller side, and the pore size of LTA-Ca 0.9 is on the larger side.

[0083] The breakthrough curves of calcium-ion-modified LTA zeolite for the n-butene / i-butene mixed gas are as Figure 8 shown. From the saturation time corresponding to C / C0 = 1 when the curve in the figure reaches, the adsorption capacity of the material for each component can be judged. It can be seen that there are obvious differences in the adsorption capacity of all calcium-ion-modified LTA zeolites for n-butene and i-butene. The saturation time of i-butene on these adsorbents is between 0.1 - 0.3 h, while the saturation time of n-butene reaches 2 - 3 h. This phenomenon is related to their micropore size. The size of the n-butene molecule is smaller and can smoothly enter the pore channels of calcium-ion-modified LTA zeolite, while the relatively larger-sized i-butene molecule has difficulty entering the pore channels and thus quickly disengages from the fixed bed, thereby achieving the purpose of purifying i-butene.

[0084] The purification efficiency of calcium-ion-modified LTA zeolite for i-butene was calculated based on the following purification efficiency calculation formula:

[0085]

[0086] where η represents the purification efficiency of the material for the purified gas (mmol / (g·h)), ν is the flow rate of the mixed gas (mL / min), V% is the molar fraction of the gas component, m is the mass of the adsorbent (g), Vm is the molar volume (22.4 L / mol), T is the time when the second component starts to break through on the adsorbent (h), C1(t) and C2(t) respectively represent the detected concentrations of the two gases at a certain time, and C0 is the initial concentration.

[0087] The purification efficiency calculated by the above formula is shown in Table 2. The purification amount of i-butene first increases and then decreases with the increase of the Ca 2+ exchange degree, and has the largest purification amount (0.7724 mmol / g) on LTA-Ca 0.3 , indicating that LTA-Ca 0.3 has greater industrial application potential among the five degrees of modified zeolites. LTA-Ca 0.3The breakthrough time of n-butene up to 1.5 h also indicates that it has more effective separation time, which can reduce the number of times of adsorbent desorption and regeneration in actual industrial applications, lower the cost of industrial production, and improve the economic benefits of production. At the same time, LTA-Ca 0.3 also has the highest isobutene purification efficiency, reaching 0.5149 mmol / (g·h), indicating that LTA-Ca 0.3 can separate high-purity isobutene gas faster and more effectively, and has great potential in the rapid industrial production of high-purity isobutene.

[0088] Purification efficiency of calcium ion modified LTA zeolite in n-butene / i-butene mixed gas table

[0089]

[0090] a Q is the purification amount of isobutene; bT2 is the time point when n-butene starts to break through; c η is the purification efficiency of isobutene.

[0091] Due to the relatively excellent adsorption and separation effect of n-butene / isobutene of LTA-Ca 0.3 a cyclic adsorption test was carried out on it, and the results are as Figure 9 shown. Figure (a) shows that after heating desorption and regeneration, the adsorption saturation time of LTA-Ca 0.3 for n-butene is in the range of 3 - 3.5 h. After multiple cycles, the saturation time of n-butene increases slightly. It is speculated that this may be because repeated heating removes trace moisture or fine impurities in the material pores, resulting in more adsorption space. This also indicates that the material has good thermal stability. Figure (b) shows the dynamic adsorption selectivity of LTA-Ca 0.3 and the change of isobutene purification efficiency in 5 cyclic adsorption processes. It can be seen that LTA-Ca 0.3 in 5 cyclic adsorption processes, the adsorption and separation ability of n-butene / isobutene and the purification effect of isobutene can be basically completely restored. After 5 cycles, it can still maintain a dynamic selectivity of 36.52 and an isobutene purification efficiency of 0.4767 mmol / (g·h), indicating that the material has good desorption and regeneration ability. Through Figure 10 the XRD comparison of the material before and after cyclic adsorption can further prove that LTA-Ca 0.3 has not been damaged in the breakthrough experiment and repeated heating and cooling, indicating that the material is very stable, suitable for repeated use, and has great economic potential and application prospects in large-scale industrial production.

[0092] Figure 9 (a) LTA-Ca at 1 bar and 298 K 0.35 - cycle breakthrough experiments of 1 - butene / iso - butene. Dashed line: iso - butene, solid line: 1 - butene; (b) Dynamic adsorption selectivity and purification efficiency of LTA - Ca 0.3 during 5 cycles.

[0093] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above - mentioned embodiments. The above - mentioned embodiments and the descriptions in the specification are only preferred examples of the present invention and are not used to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements fall within the scope of the present invention claimed. The scope of the present invention claimed is defined by the appended claims and their equivalents.

Claims

1. A preparation method of an adsorbent for the adsorption separation of 1-butene and isobutene, characterized in that, It includes the following steps: Step 1: Preparation of calcium ion-modified LTA zeolite, specifically as follows: Step 1.1: Uniformly mix 8.24 g of powdered instant sodium silicate, 6.4 g of NaOH, and 80 mL of deionized water in a beaker, stir and dissolve to obtain a transparent sodium silicate solution; Step 1.2: Mix and dissolve 6.15 g of sodium aluminate, 3.2 g of NaOH, and 40 mL of deionized water to obtain a transparent sodium aluminate solution; Step 1.3: Slowly drip the sodium silicate solution into the sodium aluminate solution, and stir and age at room temperature for 24 h to obtain a gel mixture; Step 1.4: Transfer the gel mixture to a polytetrafluoroethylene autoclave and hydrothermally treat it at 363 K for 24 h; Step 1.5: After the hydrothermal treatment, wait for the autoclave to cool to room temperature, filter out the product and wash it with deionized water until the pH is neutral; Step 1.6: Dry the solid product in an oven at 373 K for 12 h to obtain the synthesized LTA zeolite powder, named LTA-Na, which has not been modified by calcium ions yet; Step 1.7: Take out 5 g of the above-synthesized LTA zeolite powder, add it to a 0.1 mol / L calcium chloride aqueous solution, and stir at room temperature for 24 h; Step 1.8: Filter to obtain the filter residue, then add the 0.1 mol / L calcium chloride aqueous solution to the filter residue again and stir at room temperature for 24 h; Step 1.9: Filter to obtain filter residue, thoroughly wash the material with deionized water, and after washing, place it in an oven for drying. The resulting powder is the LTA-type zeolite powder modified with calcium ions, which is named LTA-Ca 0.1 ; Step 2: Based on the above-prepared calcium ion-modified LTA zeolite powder, use bentonite to bond it to prepare zeolite particles for the adsorption separation of 1-butene / iso-butene in a fixed bed, specifically including the following steps: Step 2.1: Take out a certain amount of calcium ion-modified LTA zeolite powder, add 5% of its mass of bentonite to it, and mix the two evenly; Step 2.2: Add a small amount of deionized water to the above mixed powder, stir evenly to make the mixture present a semi-fluid colloidal state; Step 2.3: Use a small spoon to dig out some of the colloidal substance and slowly roll it into small balls of appropriate size and spread them one by one on a clean polytetrafluoroethylene disc; Step 2.4: Put the disc into the oven and dry it for 6 h to obtain spherical calcium ion-modified LTA zeolite particles with a size between 3 - 5 mm; Step 3: Use the formed calcium ion-modified LTA zeolite particles for the adsorption separation of 1-butene / iso-butene. The entire adsorption separation process is carried out at a pressure of 1 bar. The flow rate of each gas is controlled by a mass flow controller (MFC). When the gas enters the adsorption column (inner diameter: 10 mm, column length: 65 mm) filled with molecular sieve for adsorption, the concentration of each component gas in its tail gas is measured by a gas chromatograph, and the final result is transmitted through an electrical signal. The specific operation steps are as follows: Step 3.1: Fill about 500 mg of molecular sieve particles into the adsorption column and ensure that the airtightness of the entire adsorption device is good; Step 3.2: Open direct-through ball valves 1 and 4, close direct-through ball valves 2 and 3, open the nitrogen switch, regulate the nitrogen flow rate to 20 mL / min, so that nitrogen purges the molecular sieve from top to bottom, heat the adsorption column, and make the molecular sieve in the adsorption column remove water and be activated in an N2 atmosphere at 423 K for 1 h; Step 3.3: After the activation is completed, stabilize the temperature of the adsorption column at 298 K, close the direct-through ball valves 1 and 4, and turn off the nitrogen gas switch. Open the switches of the n-butene and isobutene gas cylinders, control the flow rates of the two gases to be 10 mL / min respectively, open the direct-through ball valves 2 and 3, and allow the binary mixed gas to pass through the adsorption column from bottom to top (green route) for adsorption. The tail gas after adsorption enters the gas chromatograph for analysis; Step 3.4: Normalize the experimental data obtained from the gas chromatography and plot the breakthrough curve of the concentration of each component changing with time.

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